The present invention relates to generally to wood composite materials and more particularly to a process and system for obtaining a thickness swell measurement for a wood composite material sample.
Despite significant research efforts put forth over several decades and the progress made to reduce thickness swell response of wood-based composite panels, thickness swell and resulting degradation of associated panel properties remains a priority issue for the wood-based panel industry. Thickness swell in a wood composite material is recognized as having two components: (a) the normal swelling characteristics of the wood itself, and (b) the swell component that develops from the release of compression stresses in the mat which forms the wood composite material. The swell originating from the wood itself is considered recoverable; the swell originating from the release of compressive stresses is considered non-recoverable swell, and is commonly called xe2x80x9cspringbackxe2x80x9d.
Existing standard measurement methods continue to rely on changes in total thickness of a sample as measured with a single caliper instrument in the evaluation of thickness swell. A representative standard technique for measuring total thickness swell and water absorption is disclosed in a procedure set forth in ASTM 1037-92 A (1992). Summarily, total thickness swell (TS) is taken at the midpoint of each side of a wood composite sample one inch (1xe2x80x3) in from the edge using a dial caliper. Total edge thickness swell (ETS) is taken at each edge of the sample at the same mid-point location of each edge as the total thickness swell measurement is taken. Water absorption is based on weight changes of the sample at pre-selected exposure intervals.
Two representative techniques have been attempted in the art in an effort to determine thickness swell characteristics within a wood composite panel. See Xu, W. and P. M. Winistorfer, xe2x80x9cA Procedure to Determine Thickness Swell Distribution in Wood Composite Panelsxe2x80x9d, Wood and Fiber Science 27(2);119-125 (1995), and Xu. W. and P. M. Winistorfer, xe2x80x9cLayer Thickness Swell and Layer Internal Bond of Medium Density Fiberboard and Oriented Strandboardxe2x80x9d, Forest Prod. J. 45(10): 67-71 (1995).
The technique proposed by Xu and Winistorfer in Wood and Fiber Science 27(2):119-125 (1995) pertains to an intact specimen algorithm to determine thickness swell distribution across the board thickness based on vertical density distribution changes measured before and after water exposure treatment. The technique proposed by Xu and Winistorfer in Forest Prod. J. 45(10): 67-71 (1995) is a layer slicing procedure in which thin horizontal layers are sectioned from composite samples and subsequently tested for thickness swell after 24-hour water soak.
Both techniques suffer from limitations that restrict their widespread implementation as a standard protocol. The intact algorithm method requires the nondestructive measurement of density through the sample thickness. While laboratory densitometers utilizing a gamma source may be used to make measurements on standard 150xc3x97150 mm thickness swell samples, current commercial densitometers for the panelboard industry can only be utilized with standard 50xc3x9750 mm internal bond samples for density profile measurement. The same limitation applies to the layer slicing technique in that only 50xc3x9750 mm samples can be prepared with the technique, while the standard size of a wood composite sample used in thickness swell evaluation is 150xc3x97150 mm. The removal of saw kerf material adds an additional source of measurement error in the layer slicing technique. Moreover, individual layers that are removed from the intact specimen more easily absorb water and will thus swell more than or less than the intact, whole sample without the influence of internal stress.
Significantly, important information about panel material response to swell conditions and the overall resulting performance of the panel material is not revealed by existing methods. Therefore, the development of an improved process and system for evaluating the thickness swell of a wood composite material represents an ongoing and long-felt need in the art.
A process and system for obtaining a thickness swell measurement of a wood composite material sample is disclosed. The process comprises placing a measurement pattern on an edge of a wood composite material sample, the measurement pattern comprising a plurality of layers, each of the layers having a thickness; measuring the thickness of at least one of the layers of the measurement pattern prior to exposing the wood composite material sample to a thickness swell-inducing condition; exposing the wood composite material sample to a thickness swell-inducing condition; and re-measuring the thickness of the at least one layer after exposing the wood composite material sample to a thickness swell-inducing condition to thereby obtain a thickness swell measurement for the wood composite material sample.
A system suitable for use in carrying out the process of the present invention is also disclosed herein.
Accordingly, it is an object of the present invention to provide a non-destructive process for measuring and evaluating thickness swell in wood composites that provides information not previously available from existing standard measurement methods.
It is another object of the present invention to provide a non-destructive process for measuring and evaluating thickness swell in wood composites that accommodates the analysis of multiple internal layers of a wood composite material.
It is yet another object of the present invention to provide a non-destructive process for measuring and evaluating thickness swell in wood composites that provides more information than existing prior art processes about the total material response during or after completion of any of the standard water soak or high humidity exposure condition treatments used to evaluate panel stability.
It is a further object of the present invention to provide a non-destructive process for measuring and evaluating thickness swell in wood composites that can be used as an improved quality control technique for production plants.
It is yet a further object of the present invention to provide an efficient and non-destructive process for measuring and evaluating thickness swell in wood composites for the wood composite industry as a whole.
It is still a further object of the present invention to facilitate research and development of new products and improvements/modifications in product performance by providing an improved process for measuring and evaluating thickness swell in wood composites.
These and other objects are achieved in whole or in part by the invention as disclosed herein. Some of the objects of the invention having been stated hereinabove, other objects will become evident as the description proceeds, when taken in connection with the accompanying Examples and Drawings as best described hereinbelow.